This phase 2b study will evaluate the efficacy and safety of 16 and 24 weeks of response-guided duration of therapy with GS-9190 and GS-9256 in combination with Peginterferon Alfa-2a (Pegasys®) and Ribavirin (Copegus®). Additionally, the efficacy and safety of 24 weeks of GS-9256 in combination with Peginterferon Alfa-2a (Pegasys®) and Ribavirin (Copegus®) will be evaluated.